After a long day of school or work, a group of families gathers in a Stanford Hospital classroom in Menlo Park, Calif. The children are all in the highest percentile for body mass index, or BMI. They've signed up with their parents, often at the urging of a pediatrician, for a six-month healthy eating and exercise boot camp.

Gabriel Rodriguez, an 11-year-old, sparkly-eyed, self-confessed burrito lover, graduated from the program a few months ago. He's at the meeting with his mom, Gloria Arteaga, for their monthly check-in with their health coach, Thea Runyan.

They meet every month to measure Gabriel's weight and height and talk about how well he's sticking to his exercise and healthy eating goals.

The program is designed around a traffic light system. Soda and cookies are reds. Other foods are yellows or greens. Reds aren't banned, but kids do set goals for bringing down how many they eat each month. They keep track of what they eat in a journal — the snacks after soccer practice, the pizza at school.

Gabriel's chart shows he has reduced his red lights from 90 to 30 a month, and he's pretty much stuck with it.

The kids gradually cut back the amount of junk food they eat, so it doesn't feel like a big change, program director Cindy Zedeck says. This isn't a diet — a word she says they never use with kids or parents.

"You're really signing up for six months of learning how to improve your eating and exercise habits for your lifetime," she says. "It's not a diet that you're on and then you're off at the end of the six months. This will give you the tools to continue to make changes for your lifetime."

Those changes also include exercise. Kids set goals around playing or doing sports for an hour each day.

Often the hardest part for parents is figuring out how to talk to their kids about weight, Zedeck says.

"A lot of parents call and say that their child has very high self-esteem, feels very confident, is very active, but they're overweight," she says. "So they don't want to bring up their weight, because they don't want to make them feel badly about it if it's not a current concern for them."

The last thing a parent wants is to saddle a child with a self-image problem or eating disorder. So instead, Zedeck encourages parents to tell their child that the whole family could stand to be healthier, and the program is something they can do together.

There are often plenty of clues that a child actually wants help, Runyan says. For example, Gabriel asked his mom if he was fat. Other kids complain they can't keep up during soccer or basketball. But Runyan says parents, out of embarrassment or nervousness or their own issues with weight or food, can dismiss the problem.

"I think what happens when this issue comes up at home is the parent is quick to say, 'Oh, no. Nothing is wrong. Everything's fine. You are wonderful. I love you,' instead of listening and saying, 'OK, they're actually asking for help,'" she says.

The program at Stanford has an enviable success rate. Since 1999, about 80 percent of the kids who've finished have achieved their body weight goals. Although most of the families were referred by a pediatrician, health insurers won't pay for it. Instead, the costs are largely covered by grants for low-income families, while others pay out of pocket.

For Gabriel, he says being with other kids who are overweight and trying to get healthier has kept him going.

"It's not like I'm the only person in the world," he says. "I know there are other people out there like me."

For tweens and teens who are still growing, the goal is not to shed pounds but to maintain a healthy weight. Gabriel is closing in on his health goals. His weight is staying about the same, but he's growing taller and, clearly, into himself.

Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.